The molecular Zeeman effect of vinylene carbonate, maleic anhydride, acrolein and the benzene isomers, 3,4-dimethylenecyclobutene and fulvene

Publisher Website
Google Scholar
Abstract
The molecular Zeeman effect has been observed in vinylene carbonate, maleic anhydride, and acrolein yielding the molecular g values, magnetic susceptibilityanisotropies, molecular quadrupole moments, and other magnetic parameters. The susceptibility results are compared with a number of other open‐ring compounds and nonconjugated ring compounds in order to establish a set of group magnetic susceptibilityanisotropies which can be added to give the molecular magnetic susceptibilityanisotropy. The group values of the out‐of‐plane minus the average in‐plane susceptibility are (in units of 10 −6 erg/G 2 · mole ): – – – C – (sp 3 carbon )=1.6 ± 0.8, = C (sp 2 carbon ) = −4.4 ± 0.4, – – = O ( carbonyl oxygen )=−6.5 ± 0.7, and O ( ether oxygen )=2.0 ± 1.5. – – The appropriate sum of these values is in good agreement with experiment on a large number of molecules. The rotational molecular Zeeman effect has also been observed in 3,4‐dimethylenecyclobutene and fulvene. For 3,4‐dimethylenecyclobutene, the g values are g aa =−0.0703 ± 0.0007, g bb =−0.0532 ± 0.0007 , and g cc =0.0023 ± 0.0007 , the magnetic susceptibilityanisotropies (in units of 10 −6 erg/G 2 · mole ) are 2χ aa −χ bb −χ cc =22.1 ± 0.7 and 2χ bb −χ cc −χ aa =21.2 ± 0.6 , and the molecular quadrupole moments (in units of 10−26 esu cm2) are Q aa =4.0± 1.2, Q bb =4.0± 1.2 , and Q cc =−8.0± 1.8 where the a and b axes are in the plane and the b axis is the dipole moment axis. For fulvene, the g values are g aa =−0.1059 ± 0.0014, g bb =−0.0482 ± 0.0007 , and g cc =0.0219 ± 0.0007 ; the magnetic susceptibilityanisotropies (in units of 10 −6 erg/G 2 · mole ) are 2χ aa −χ bb −χ cc =35.9 ± 0.7 and 2χ bb −χ aa −χ cc =38.1 ± 1.1 ; and the molecular quadrupole moments (in units of 10−26 esu cm2) are Q aa =5.8 ± 1.4, Q bb =3.6 ± 1.6 , and Q cc =−9.4 ± 2.1 , where the a and b axes are in the plane and the a axis is the dipole axis. The Zeeman parameters in these two molecules are compared to benzene and other ring compounds by the use of the local groupanisotropies determined from the open‐ring and nonconjugated ring compounds as described above.